The present invention is directed to industrial filtration systems and, more particularly, to a technique for cleaning air filters of the type which are utilized to collect textile waste such as dust, lint, fibrous materials and the like from airstreams contaminated therewith. The air filters of the present invention are so constructed as to be mounted in a pair and subjected to a backflow of air therethrough induced by the same high vacuum pump that generates the normal airflow path.
Modern industrial environments require conditioning of the air space therein from the standpoint of several characteristics. Various reasons exist behind these conditioning requirements. Often the manufacturing or industrial operations being carried on in the workplace dictate a certain temperature, humidity, or maximum level of contaminants in the air. Health and safety regulations now require that the environment in which workers perform their tasks be free of unhealthy contaminants. Textile lint and waste is considered to be one of the most dangerous of these contaminants which should be removed. If the various areas on which lint and waste collect can be automatically cleaned and the lint, waste and dust removed, it is less likely to become entrained in the air and thus become a health hazard to personnel.
One specific example of an industrial application in which recent health and safety standards have required a reduction in the level of airborne particulates is in the processing of cotton. For decades cotton mills, in which raw cotton is opened, combed, carded and spun into yarn, have been one of the most contaminated, unhealthy environments in which an industrial worker could possibly exist. Numerous cases of brown lung traced their causes to the cotton mill. Other industrial environments are similarly required to be cleaned in accordance with contemporary health and safety standards. In such environments as the cotton mill, the amount of lint, waste, fibers, and dust generated is of such magnitude that continuous cleaning and filtering of the air is required. The airstream which is generated to collect and entrain such contaminants from various places is delivered to some type of filter or collection system. The entire system conceptually resembles a large vacuum cleaner with a plurality of pickup heads. Lint, waste, fibers, and dust are continuously picked up from various points and transmitted to one or more filter apparatuses or "receivers" where the air entrained solid constituents are separated from the airstream by a filter screen. The clean air is then exhausted and the solid constituents collected.
In some systems, it has become an accepted practice to use a high vacuum pump to generate a sufficient vacuum to pick up such constituents from various places throughout the factory. The contaminants are carried through a conduit and delivered to one of two receivers or filter chambers which are loaded evenly and alternatively. The output of each receiver is connected to the high vacuum pump, so that the same pump brings in contaminated air to both receivers and exhausts air therefrom. In such embodiments, it is necessary to periodically dump the solid constituents collected on the screen and backflush the screen. In known systems, such backflushing has occurred or been effected by the use of compressed air from separate sources.
In the past, filter apparatuses have been utilized in which a dirty air stream is delivered to one of two or more filter sections of a filter housing. By some type of baffling system, alternate sections of the housing are used for collection, while other portions of the housing are backflushed by a separate energy source. Examples of such systems are illustrated in U.S. Pat. No. 4,778,491 to Yow; U.S. Pat. No. 4,372,713 to Kean, Jr.; U.S. Pat. No. 729,527 to Titgen; and British Patent No. 546,878 to Thomas Ash & Company. One other system is illustrated in British Patent No. 778,537 to Klockner et al. in which is shown two separate passageways, each of which includes a filter. During normal operation, the dirty airstream passes in one direction, however, during the cleaning operation, air is passed in the opposite direction to backflush the screen. However, a separate blower 24 is utilized for backflushing while a vacuum fan is used for normal operation. This is the type of system referred to earlier in which separate energy sources are used for the cleaning operation and the backflushing operation.
In one other approach described in U.S. Pat. Nos. 1,493,110 to Diehl and 2,836,256 to Caskey, parallel filter paths are established. Then a portion of the outflowing air, downstream of the filter screen, is diverted back to be used in a backflushing operation for the other screen. This has proven to be inadequate as far as providing sufficient suction for efficient backflushing operations in which the cleaned screen is not only backflushed, but the resulting airstream therefrom is to be diverted to and through the other filter chamber.